Many believe that keeping the ball low in the zone keeps the ball in the park. Thing is ... I've seen plenty of HRs off of pitches low in the zone.
Are these commentators correct when they preach keeping the ball low in the zone? Is it a function of the batter? Let's say a hitter has grooved a good barrel path that will result in a steeper, more diagonal barrel, at impact, for a ball lower in the zone. Wouldn't this increase the probability of getting the ball in the air?
Yes, that does stand to reason. In fact, my DD has been working to move toward getting a little steeper/more diagonal at impact. In practice, she gets it and can launch those low ones. She has a teammate who does that very well (might call it a ferris-wheel swing) and hits bombs off low pitches off some really good pitchers.
My guess is that if you're facing hitters who've mastered that sort of swing, staying low might not be so wise. Most hitters I see in travel ball don't get that concept and swing more 'level' and have trouble digging out low balls, especially if those that have good downward movement.